hello could you help me please to understand this subject because Ihave exam on 16th of january An operating system normally manages the execution of several processes held simultaneously in main and secondary memory. One of the goals of an operating system is to optimise performance by making efficient use of the CPU time and memory space. Describe in two the different ways in which the operating system can help achieve this goal. Diagrams and a bibliography may occupy additional space. Thanks

efficient scheduling might be one of the possibilities

There should be appropriate discussions in your text book. Regarding the CPU, you might look for discussions of prioritization, scheduling, time slicing, etc. Regarding memory, you might look for discussions of paging, and/or swapping, and perhaps the phrase "least recently used".